1. Field of the Invention
The present invention relates to a superconductor of a ceramic superconductive material and a method of preparing the same.
2. Description of the Background Art
Ceramic superconductive materials have been recently watched with interest as materials which exhibit high critical temperatures. In order to obtain a superconductor having a desired configuration from such a ceramic superconductive material, a sintering method of press-molding a raw material of ceramic powder and thereafter sintering the same is generally employed.
However, in such a sintering method, it is difficult to obtain a dense superconductor because of voids resulting from compression molding of the powder material, and hence improvement of superconducting properties is restricted.
Reports by R. S. Feigelson et al., SCIENCE vol. 240, 17 June 1988, pp. 1642-1645 and by G. F. de la Fuente et al., MRS SPRING MEETING, April 1989 each disclose a method of preparing a superconductor such as a Bi--Sr--Ca--Cu--O ceramic superconductor or a Bi--Pb--Sr--Ca--Cu--O superconductor in the form of fiber by a laser pedestal growth method.
However, in the conventional method of preparing a Bi--Sr--Ca--Cu--O ceramic superconductor using the laser pedestal growth method, the growth rate must be reduced in order to align superconducting phases. Thus, this method is has inferior productivity in terms of application to a wire or the like. Further, although a Bi--Sr--Ca--Cu--O ceramic superconductor obtained according to the conventional method attains a high critical current density (J.sub.c) in a zero magnetic field, the critical current density is reduced in a magnetic field. Such a phenomenon causes a significant problem in application to a magnet or the like, which is used in a magnetic field.